First, please remove the aerator from the kitchen sink faucet and see if the water works better. Cleaning and/or replacement of the aerator will help many times.
Second, on some old homes plumbed with copper pipe, the angle stops were installed using galvanized pipe nipples through the wall. Replacing these with new brass nipples, new stops and new supply tubes could help. Many times (30 years! ) these things are plugged. For this I would recommend a plumber. If the fitting behind the wall breaks during replacement of the nipple, then soldering in the wall may be required.